Run results for: Spread vs mutating

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.13; rv:62.0) Gecko/20100101 Firefox/62.0

Browser: Firefox 62

Operating system: Mac OS X 10.13

Device Platform: Desktop

Date tested: 6 years ago

Test name	Executions per second
Spread operator	18.9 Ops/sec
Mutate accumulator	61994.5 Ops/sec

Script Preparation code:

var array = Array.from(Array(1000).keys());

Tests:

Spread operator
array.reduce((acc, number) => ({ ...acc, [number]: null }), {});
Mutate accumulator
array.reduce((acc, number) => { acc[number] = null; return acc; }, {});